An anti-freezing control method and an air-conditioning heat exchange system

Abstract

The present invention provides an anti-freezing control method and an air-conditioning heat exchange system. The anti-freezing control method includes: when the air-conditioning main unit operates in a defrosting mode and the refrigerant temperature T3 is lower than the first preset value T a , adjusting the water pump flow rate and / or the compressor frequency of the air-conditioning main unit according to the refrigerant temperature T3 and the outlet water temperature T2 of the plate heat exchanger; when the air-conditioning main unit operates in a defrosting mode and the refrigerant temperature is higher than the first preset value T a , adjusting the power of the electric heating according to the outlet water temperature T1 of the electric heating device and the user-set temperature T 设 . The control method of the present invention prevents the refrigerant with too low temperature from entering the plate heat exchanger. At the same time, when both the refrigerant temperature and the outlet water temperature of the plate heat exchanger are relatively low, the compressor of the air-conditioning main unit is timely controlled to stop. When the refrigerant temperature is relatively low and the outlet water temperature of the plate heat exchanger is relatively high, the anti-freezing protection of the plate heat exchanger can be achieved only through the water flow rate. While fully preventing the plate heat exchanger from cracking, it avoids resource waste and improves the energy efficiency of the air-conditioning heat exchange system.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioners, and in particular, to an anti-freezing control method and an air conditioner heat exchange system. Background Art

[0002] In the residential power consumption system, the demands for water heaters and air conditioners account for a relatively large proportion of the energy consumption. Under normal circumstances, the two often operate independently of each other, lacking effective combination and wasting energy. Therefore, a new type of air conditioner system that combines a water heater and an air conditioner has begun to appear on the market. When in use, the refrigerant in the air conditioner main unit and the water from the water pump exchange heat in the plate heat exchanger, and the water can be heated. When heating the water, the air conditioner main unit operates in the heating mode. When the outdoor ambient temperature is low and the humidity is high, frost will form on the fins of the main unit, reducing the heat exchange performance. The existing air conditioner will switch modes: that is, switch from the heating mode to the cooling mode for defrosting. During the cooling defrosting process, the temperature of the refrigerant entering the plate heat exchanger is too low, which may cause the plate heat exchanger to freeze and crack. Therefore, anti-freezing measures need to be taken.

[0003] A common practice in the prior art is to provide an electric heating device on the outlet water pipeline of the plate heat exchanger, and a temperature sensor is provided downstream of the electric heating to detect the outlet water temperature after being heated by the electric heating. When the outlet water temperature is too low, it indicates that the water temperature in the plate heat exchanger is relatively low, and at this time, the air conditioner main unit is controlled to stop. However, this protection method in the prior art is not timely, and it judges the water temperature in the plate heat exchanger based on the temperature after electric heating, and cannot accurately reflect the temperature of the plate heat exchanger in a timely manner, resulting in a potential risk of freezing and cracking of the plate heat exchanger. Summary of the Invention

[0004] In view of this, the present invention aims to propose an anti-freezing control method and an air conditioner heat exchange system to solve the problem that the plate heat exchanger in the prior art is easily frozen and cracked, affecting the normal use of the air conditioner.

[0005] To achieve the above object, the technical solution of the present invention is realized as follows:

[0006] An anti-freezing control method for anti-freezing control of a plate heat exchanger in an air conditioner heat exchange system, the anti-freezing control method comprising:

[0007] When the air conditioner main unit operates in the defrosting mode and the refrigerant temperature T3 is lower than the first preset value T a , adjust the water pump flow rate and / or the compressor frequency of the air conditioner main unit according to the refrigerant temperature T3 and the outlet water temperature T2 of the plate heat exchanger;

[0008] When the air conditioner main unit operates in the defrosting mode and the refrigerant temperature is higher than the first preset value T a , enter the hot water stable mode;

[0009] The hot water stable mode is to adjust the power of the electric heating according to the outlet water temperature T1 of the electric heating device and the user-set temperature T 设 When the air conditioner performs reverse defrosting, it detects the refrigerant temperature entering the plate heat exchanger in advance according to the temperature of the refrigerant inlet of the plate heat exchanger. When the refrigerant temperature is too low, it starts the anti-freezing protection for the plate heat exchanger in time to prevent the refrigerant with too low temperature from entering the plate heat exchanger. At the same time, when both the refrigerant temperature and the outlet water temperature of the plate heat exchanger are relatively low, it controls the air conditioner main unit compressor to stop in time. When the refrigerant temperature is relatively low and the outlet water temperature of the plate heat exchanger is relatively high, the anti-freezing protection of the plate heat exchanger can be achieved only through the water flow rate. While fully preventing the plate heat exchanger from cracking, it avoids waste of resources and improves the energy efficiency of the air conditioner heat exchange system.

[0010] Further, when the refrigerant temperature T3 is between the first preset value T a and the second preset value T b , T b <T a , the compressor frequency F is reduced to increase the refrigerant temperature of the plate heat exchanger. When T3 is between the first preset value T a and the second preset value T b , it indicates that the temperature at the refrigerant inlet of the plate heat exchanger is relatively low, but it will not cause the plate heat exchanger to crack in a short time. At this time, the compressor frequency F is reduced to increase the refrigerant inlet temperature of the plate heat exchanger, thereby reducing the risk of the plate heat exchanger cracking.

[0011] Further, when the refrigerant temperature T3 rises above the first preset value T a , the compressor operates at the current frequency, and the plate heat exchanger operates in the hot water stable mode; when the refrigerant temperature T3 does not exceed the first preset value T a , the compressor frequency F is continuously reduced. When the compressor frequency F is reduced below the minimum operating frequency F min , the air conditioner main unit is controlled to stop.

[0012] Further, the compressor frequency F is adjusted in real time according to the refrigerant temperature T3, F = F0×(1 - T3 / T a ).

[0013] Further, when the refrigerant temperature T3 is lower than the second preset value T b , the start and stop of the compressor and the water pump flow rate are adjusted according to the outlet water temperature T2 of the plate heat exchanger.

[0014] Further, when the outlet water temperature T2 of the plate heat exchanger does not exceed the fifth preset value T m , the air conditioner main unit is controlled to stop and the water pump stops supplying water; when the outlet water temperature T2 of the plate heat exchanger exceeds the fifth preset value T mWhen it is, control the air-conditioning main unit to stop and increase the water pump flow rate. If the outlet water temperature T2 of the plate heat exchanger is lower than the fifth preset value T m When it is, it indicates that the water temperature entering the plate heat exchanger is relatively low. At this time, either the extremely low temperature refrigerant or the low temperature water entering the plate heat exchanger is likely to cause the plate heat exchanger to freeze and crack. Therefore, control the air-conditioning main unit to stop and the water pump to stop supplying water to prevent the refrigerant and water from entering the interior of the plate heat exchanger. When the refrigerant temperature T3 is extremely low, but the outlet water temperature T2 of the plate heat exchanger is relatively high, that is, T2 exceeds the fifth preset value T m When it is, it indicates that the water temperature entering the plate heat exchanger is not likely to cause the plate heat exchanger to freeze and crack. At this time, the air-conditioning main unit can be controlled to stop to stop the refrigerant from entering the plate heat exchanger, and at the same time, the water pump flow rate can be increased to increase the water flow rate entering the plate heat exchanger, so as to increase the average water temperature in the plate heat exchanger and reduce the risk of the plate heat exchanger freezing and cracking.

[0015] Furthermore, the hot water stable mode includes:

[0016] When T c ≤T1<T 设 According to the outlet water temperature T1, the set temperature T 设 And the third preset value T c Adjust the power P of the electric heating device in real time, P = P0×[1+(T 设 -T1) / (T 设 -T c )];

[0017] When T1<T c Control the air-conditioning main unit to stop, and adjust the power P of the electric heating device according to the outlet water temperature T1, the set temperature T 设 And the third preset value T c P = P0×[1+(T 设 -T1) / (T 设 -T c )];

[0018] When T 设 ≤T1<T d Reduce the electric heating power P = P0×[1-(T1-T 设 ) / (T d -T 设 )];

[0019] When T1≥T 设 Turn off the electric heating.

[0020] Furthermore, the third preset value T c Is set to be less than T 设 , The difference between the third preset value T c And T 设 Is 5 to 15°C.

[0021] Further, the fourth preset value T d is set to be greater than T 设 , and the difference between the fourth preset value T d and T 设 is 2 to 10 °C.

[0022] Compared with the prior art, the anti-freezing control method of the present invention has the following advantages:

[0023] When the air conditioner performs reverse defrosting, it detects the temperature of the refrigerant entering the plate heat exchanger in advance according to the temperature at the refrigerant inlet of the plate heat exchanger. When the refrigerant temperature is too low, it starts anti-freezing protection for the plate heat exchanger in time to prevent the refrigerant with too low temperature from entering the plate heat exchanger. At the same time, when both the refrigerant temperature and the water temperature at the outlet of the plate heat exchanger are relatively low, it controls the compressor of the air conditioner host to stop in time. When the refrigerant temperature is relatively low and the water temperature at the outlet of the plate heat exchanger is relatively high, anti-freezing protection for the plate heat exchanger can be achieved only through the water flow rate. While fully preventing the plate heat exchanger from cracking, it avoids waste of resources and improves the energy efficiency of the air conditioner heat exchange system.

[0024] The present invention also provides an air conditioner heat exchange system capable of executing the above-mentioned anti-freezing control method. The air conditioner heat exchange system includes an air conditioner host, a plate heat exchanger, a water pump, and an electric heating device. A water pump is provided at the water inlet end of the plate heat exchanger, an electric heating device is provided on the water outlet pipeline of the plate heat exchanger, a third temperature sensor is provided on the inlet pipeline of the plate heat exchanger, and the third temperature sensor is provided at the refrigerant inlet of the plate heat exchanger or a position close to the inlet. A second temperature sensor is provided on the water outlet pipeline between the plate heat exchanger and the electric heating device, and the second temperature sensor is provided at a position close to the water outlet of the plate heat exchanger. An outlet water temperature sensor is also provided at the water outlet end of the electric heating device.

[0025] The air conditioner heat exchange system has the same advantages as the above-mentioned anti-freezing control method compared with the prior art, and will not be elaborated here. Description of the Drawings

[0026] Figure 1 is a schematic structural diagram of the air conditioner heat exchange system according to the embodiment of the present invention;

[0027] Figure 2 is a flowchart of the anti-freezing control method according to the embodiment of the present invention.

[0028] Figure 3 is a flowchart of the hot water stable mode control according to the embodiment of the present invention.

[0029] Description of the Reference Numerals:

[0030] 100 - Air conditioner main unit, 101 - Inlet pipeline, 102 - Discharge pipeline, 103 - Third temperature sensor, 200 - Water pump, 300 - Plate heat exchanger, 301 - Outlet water pipeline, 302 - Second temperature sensor, 303 - Inlet water pipeline, 400 - Electric heating device, 401 - Outlet water temperature sensor Detailed implementation manners

[0031] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of specific embodiments of the present invention is provided in conjunction with the accompanying drawings.

[0032] As shown in the figure, the present embodiment provides an anti - freezing control method for anti - freezing control of a plate heat exchanger in an air - conditioner heat - exchange system. Specifically, the control method includes the following steps:

[0033] S100. When the air - conditioner main unit operates in the defrosting mode and the refrigerant temperature T3 is lower than the first preset value T a At this time, adjust the water - pump flow rate and / or the compressor frequency of the air - conditioner main unit according to the refrigerant temperature T3 and the outlet water temperature T2 of the plate heat exchanger. The refrigerant temperature T3 is the temperature at the refrigerant inlet of the plate heat exchanger.

[0034] Specifically, when the air - conditioner main unit operates in the defrosting mode, the air conditioner reverses to refrigerate. At this time, the compressor of the air - conditioner main unit operates at the initial frequency F0. The refrigerant temperature T3 entering the plate heat exchanger is relatively low. It is necessary to increase the refrigerant temperature T3 entering the plate heat exchanger and / or control the water temperature entering the plate heat exchanger to prevent the temperature of the plate heat exchanger from being too low.

[0035] The first preset value T a Is set according to the refrigerant temperature that will not cause the plate heat exchanger to freeze. Preferably, the first preset value T a Is set to 3 - 10 °C. More preferably, the first preset value T a Is set to 5 °C.

[0036] When the refrigerant temperature T3 is between the first preset value T a And the second preset value T b It indicates that the temperature at the refrigerant inlet of the plate heat exchanger is relatively low, but it will not cause the plate heat exchanger to freeze in a short time. At this time, by reducing the compressor frequency F, the refrigerant inlet temperature of the plate heat exchanger is increased, thereby reducing the risk of the plate heat exchanger freezing. Among them, T b <T a . The second preset value T b Is set to - 2 - 2 °C. More preferably, the second preset value T b Is set to 0 °C.

[0037] Further, during the process of reducing the compressor frequency, continuously detect the refrigerant temperature T3. At this time, the refrigerant temperature T3 gradually increases. When the refrigerant temperature T3 rises to the first preset value T a above, it indicates that there is no longer a risk of freezing and cracking of the plate heat exchanger. At this time, the compressor operates at the current frequency, and the plate heat exchanger operates in the hot water stable mode. When the refrigerant temperature T3 does not exceed the first preset value T a , control the compressor frequency F to continue to decrease. When the compressor frequency F decreases to the minimum operating frequency F min or below, control the air-conditioning main unit to shut down. At this time, control the temperature of the hot water through the electric heating device.

[0038] Among them, the compressor frequency F is adjusted in real time according to the refrigerant temperature T3, that is, F = F0×(1 - T3 / T a ). After the compressor frequency F starts to decrease, as the refrigerant temperature T3 rises, the compressor frequency becomes smaller and smaller. When the compressor frequency F decreases to the minimum operating frequency F min or below, control the air-conditioning main unit to shut down. At this time, control the temperature of the hot water through the electric heating device. When the refrigerant temperature T3 rises to the first preset value T a above, and the compressor frequency F is greater than the minimum operating frequency F min , it indicates that the current refrigerant entering the plate heat exchanger is not likely to cause freezing and cracking of the plate heat exchanger. At this time, control the air-conditioning main unit to operate at the current frequency and operate in the hot water stable mode at the same time.

[0039] When the refrigerant temperature T3 is lower than the second preset value T b , it indicates that the refrigerant temperature is extremely low. At this time, it is necessary to adjust the start and stop of the compressor and the water pump flow according to the outlet water temperature T2 of the plate heat exchanger. If the outlet water temperature T2 of the plate heat exchanger is lower than the fifth preset value T m , it indicates that the water temperature entering the plate heat exchanger is relatively low. At this time, either the extremely low temperature refrigerant or the low temperature water entering the plate heat exchanger is likely to cause freezing and cracking of the plate heat exchanger. Therefore, control the air-conditioning main unit to shut down and the water pump to stop supplying water to prevent the refrigerant and water from entering the inside of the plate heat exchanger. When the refrigerant temperature T3 is extremely low, but the outlet water temperature T2 of the plate heat exchanger is relatively high, that is, T2 exceeds the fifth preset value T m , it indicates that the water temperature entering the plate heat exchanger is not likely to cause freezing and cracking of the plate heat exchanger. At this time, the air-conditioning main unit can be controlled to shut down to stop the refrigerant from entering the plate heat exchanger, and at the same time, increase the water pump flow to increase the water flow entering the plate heat exchanger to increase the average water temperature in the plate heat exchanger and reduce the risk of freezing and cracking of the plate heat exchanger.

[0040] Further, the fifth preset value T m is set to 3 - 10°C. More preferably, the fifth preset value T m is set to 5°C.

[0041] S200. When the air conditioner main unit operates in the defrosting mode and the refrigerant temperature is higher than the first preset value T a , enter the hot water stable mode, and adjust the power of the electric heating device according to the outlet water temperature T1 of the electric heating device and the user-set temperature T 设 to provide continuous and stable hot water.

[0042] Among them, when the outlet water temperature T1 of the electric heating device is between the set temperature T 设 and the third preset value T c , adjust the power P of the electric heating device in real time according to the outlet water temperature T1, the set temperature T 设 and the third preset value T c . Preferably, the power P of the electric heating device = P0×[1+(T 设 - T1) / (T 设 - T c )].

[0043] The third preset value T c is set to be less than T 设 , and the third preset value T 设 is set according to the magnitude of T c in the actual use process. Preferably, the difference between the third preset value T c and T 设 is 5 - 15°C, and preferably, the difference is 10°C.

[0044] Specifically, when T c ≤ T1 < T 设 , it indicates that the outlet water temperature T1 of the electric heating device is not much different from the set temperature. At this time, the low-temperature refrigerant in the plate heat exchanger will not cause the plate heat exchanger to freeze and crack, and the temperature reduction of the water after passing through the plate heat exchanger is still within the controllable range. At this time, by increasing the power of the electric heating device, the control of the outlet water temperature can be achieved, and stable hot water can be provided to the user. P = P0×[1+(T 设 - T1) / (T 设 - T c )].

[0045] When T1 < T c , it indicates that the outlet water temperature of the electric heating device is extremely low. At this time, the low-temperature refrigerant in the plate heat exchanger further absorbs the heat in the water after the water passes through the plate heat exchanger, affecting the outlet water temperature at the final outlet end. At this time, if the low-temperature refrigerant continues to enter the plate heat exchanger, it will have a greater impact on the outlet water temperature. Therefore, the air conditioner main unit is controlled to stop. Adjust the power P of the electric heating device according to the outlet water temperature T1, the set temperature T 设 and the third preset value T c : P = P0×[1+(T 设 - T1) / (T 设 - T c )].

[0046] When the outlet water temperature T1 of the electric heating device is between the set temperature T 设 and the fourth preset value T d , that is, when T 设 ≤T1<T d , it indicates that the outlet water temperature of the electric heating device meets the user's set temperature requirement and is slightly higher than the user's set temperature. At this time, it is necessary to gradually reduce the electric heating power P = P0×[1 - (T1 - T 设 ) / (T d - T 设 ). The fourth preset value T d is set to be greater than T 设 . According to the size of T 设 in the actual use process, the fourth preset value T d is set. Preferably, the difference between the fourth preset value T d and T 设 is 2 - 10°C, and preferably, the difference is 5°C.

[0047] When T1≥T 设 , it indicates that the outlet water temperature of the electric heating device is relatively high, and the electric heating is turned off to achieve energy conservation.

[0048] The anti-freezing control method provided by the present invention enables the air conditioner to detect the refrigerant temperature entering the plate heat exchanger in advance according to the temperature at the refrigerant inlet of the plate heat exchanger when performing reverse defrosting, start anti-freezing protection for the plate heat exchanger in time when the refrigerant temperature is too low, prevent the refrigerant with too low temperature from entering the plate heat exchanger, and at the same time, when both the refrigerant temperature and the water temperature at the outlet of the plate heat exchanger are relatively low, control the air conditioner main compressor to stop in time. When the refrigerant temperature is relatively low and the water temperature at the outlet of the plate heat exchanger is relatively high, the anti-freezing protection of the plate heat exchanger can be achieved only through the water flow rate, fully preventing the plate heat exchanger from cracking and avoiding resource waste, and improving the energy efficiency of the air conditioner heat exchange system.

[0049] In the embodiment of the present invention, after controlling the air conditioner to stop, an ordinary defrosting control method without reverse defrosting is run.

[0050] As part of the embodiment of the present invention, the anti-freezing control method specifically includes the following processes:

[0051] S101. The air conditioner operates in the reverse defrosting mode, and the initial operating frequency of the compressor is F0;

[0052] S102. When the refrigerant temperature T3 is between the first preset value T a and the second preset value T b , reduce the compressor operating frequency F, F = F0×(1 - T3 / T a );

[0053] S1021. Determine whether the current operating frequency of the compressor is less than the minimum operating frequency F min , if so, execute step S1022; if not, execute step S1023;

[0054] S1022. Shut down the air conditioner main unit;

[0055] S1023. Determine whether the current refrigerant temperature T3 is above the first preset value T a . If so, execute the hot water stable mode of S200; if not, continue to reduce the compressor frequency.

[0056] S103. When the refrigerant temperature T3 does not exceed the second preset value T b , determine whether the outlet water temperature T2 of the plate heat exchanger is less than the fifth preset value T m . If so, execute step S1032; if not, execute step S1031;

[0057] S1031. Shut down the compressor and increase the flow rate of the water pipe pump;

[0058] S1032. Shut down the compressor and stop the water pump from supplying water;

[0059] S200. When the refrigerant temperature is higher than the first preset value T a , enter the hot water stable mode.

[0060] As part of an embodiment of the present invention, the hot water stable mode specifically includes the following process:

[0061] S201. When T1 < T c , shut down the air conditioner main unit and then execute step S2021;

[0062] S202. When T c ≤ T1 < T 设 , execute step S2021;

[0063] S2021. Adjust the power P of the electric heating device = P0 × [1 + (T 设 - T1) / (T 设 - T c )];

[0064] S203. When T 设 ≤ T1 < T d , execute step S2031;

[0065] S2031. Adjust the power PP of the electric heating device = P0 × [1 - (T1 - T 设 ) / (T d - T 设 )];

[0066] S204. When T1 ≥ T 设 execute step S2041;

[0067] S2041. Turn off the electric heating.

[0068] As part of an embodiment of the present invention, an air-conditioning heat exchange system is also provided, which can execute the above-mentioned anti-freezing control method. The air-conditioning heat exchange system includes an air-conditioning main unit 100, a plate heat exchanger 300, a water pump 200, and an electric heating device 400. The air-conditioning main unit 100 is connected to the plate heat exchanger 300 through a refrigerant pipeline. The refrigerant in the air-conditioning main unit 100 can enter the plate heat exchanger 300 through the refrigerant inlet pipeline 101, and after exchanging heat with the water in the plate heat exchanger 300, the refrigerant returns to the air-conditioning main unit through the refrigerant outlet pipeline 102.

[0069] A water pump 200 is provided at the water inlet end of the plate heat exchanger 300 to control the water flow rate flowing through the plate heat exchanger 300. An electric heating device 400 is provided on the water outlet pipeline 301 of the plate heat exchanger 300, and the water discharged from the plate heat exchanger 300 is further heated by the electric heating device 400.

[0070] A third temperature sensor 103 is provided on the inlet pipeline 101 of the plate heat exchanger 300. The third temperature sensor 103 is arranged at the refrigerant inlet of the plate heat exchanger 300 or a position close to the inlet to detect the temperature of the refrigerant inlet of the plate heat exchanger 300. A second temperature sensor 302 is provided on the water outlet pipeline 301 between the plate heat exchanger 300 and the electric heating device 400. The second temperature sensor 302 is arranged at a position close to the water outlet of the plate heat exchanger 300.

[0071] An outlet water temperature sensor 401 is further provided at the water outlet end of the electric heating device 400 to detect the outlet water temperature after being heated by the electric heating device 400.

[0072] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. An anti-freezing control method for anti-freezing control of a plate heat exchanger in an air-conditioning heat exchange system, characterized in that, The anti-freezing control method includes: When the air conditioner main unit operates in the defrosting mode and the refrigerant temperature T3 is lower than the first preset value T a , the water pump flow rate and / or the compressor frequency of the air conditioner main unit are adjusted according to the refrigerant temperature T3 and the outlet water temperature T2 of the plate heat exchanger; When the air conditioner main unit operates in the defrosting mode and the refrigerant temperature is higher than the first preset value T a , it enters the hot water stable mode; The hot water stable mode is to adjust the power of the electric heating according to the outlet water temperature T1 of the electric heating device and the user-set temperature T 设 The hot water stable mode includes: At T c ≤ T1 < T 设 According to the outlet water temperature T1, the set temperature T 设 and the third preset value T c Adjust and increase the power P of the electric heating device in real time; When T1 < T c the air-conditioning main unit is controlled to stop, and according to the outlet water temperature T1, the set temperature T 设 and the third preset value T c the power of the electric heating device is adjusted and increased as P = P0 × [1 + (T 设 - T1) / (T 设 - T c )]; At T 设 ≤ T1 < T d When, reduce the electric heating power P = P0 × [1 - (T1 - T 设 )) / (T d - T 设 ) When T1≥T 设 turn off the electric heating.

2. The anti-freezing control method according to claim 1, wherein When the refrigerant temperature T3 is between the first preset value T a and the second preset value T b , T b <T a , the refrigerant temperature of the plate heat exchanger is increased by reducing the compressor frequency F.

3. The anti-freezing control method according to claim 2, characterized in that, The refrigerant temperature T3 rises to the first preset value T a When above, the compressor operates at the current frequency, and the plate heat exchanger operates in the hot water stable mode; when the refrigerant temperature T3 does not exceed the first preset value T a , control the compressor frequency F to continuously decrease. When the compressor frequency F decreases to the minimum operating frequency F min , control the air-conditioning main unit to shut down.

4. The anti-freezing control method according to claim 2, wherein The compressor frequency F is adjusted in real time according to the refrigerant temperature T3, and F = F0 × (1 - T3 / T a ) 5. The anti-freezing control method according to claim 1, characterized in that When the refrigerant temperature T3 is lower than the second preset value T b the start / stop of the compressor and the flow rate of the water pump are adjusted according to the outlet water temperature T2 of the plate heat exchanger.

6. The anti-freezing control method according to claim 5, characterized in that When the outlet water temperature T2 of the plate heat exchanger does not exceed the fifth preset value T m control the air-conditioning main unit to stop and the water pump to stop supplying water; when the outlet water temperature T2 of the plate heat exchanger exceeds the fifth preset value T m control the air-conditioning main unit to stop and increase the water pump flow rate.

7. The anti-freezing control method according to claim 1, wherein The third preset value T c is set to be less than T 设 , and the third preset value T c has a difference of 5 to 15 °C from T 设 .

8. The anti-freezing control method according to claim 1, characterized in that The fourth preset value T d is set to be greater than T 设 , and the fourth preset value T d and T 设 have a difference of 2 to 10 °C.

9. An air-conditioning heat exchange system, characterized in that, Capable of implementing the anti-freezing control method described in any one of claims 1 to 8, the air-conditioning heat exchange system includes an air-conditioning main unit (100), a plate heat exchanger (300), a water pump (200), and an electric heating device (400). A water pump (200) is provided at the water inlet end of the plate heat exchanger (300), an electric heating device (400) is provided on the outlet pipeline (301) of the plate heat exchanger (300), a third temperature sensor (103) is provided on the inlet pipeline (101) of the plate heat exchanger (300), and the third temperature sensor (103) is provided at the refrigerant inlet of the plate heat exchanger (300) or a position close to the inlet. A second temperature sensor (302) is provided on the outlet pipeline (301) between the plate heat exchanger (300) and the electric heating device (400), and the second temperature sensor (302) is provided at a position close to the water outlet of the plate heat exchanger (300). An outlet water temperature sensor (401) is further provided at the water outlet end of the electric heating device (400).

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